1. Technical Field
The present invention relates to a SOI substrate and a method of manufacturing the same.
2. Related Art
Recently, a silicon-on-insulator (hereinafter, SOI) substrate has come to be more extensively employed as a semiconductor substrate for a semiconductor device. The SOI substrate includes a supporting substrate, an insulating layer provided on the supporting substrate, and a silicon layer provided on the insulating layer. The SOI substrate allows electrically isolating semiconductor chips such as transistors provided on the silicon layer, completely. Accordingly, the SOI substrate is superior to a bulk silicon substrate in level of integration, power saving, operation speed and so on.
Conventional SOI substrates include the one having a gettering site provided in the supporting substrate. The gettering site serves as a region for gettering a contaminant such as a heavy metal.
Japanese Laid-open patent publications No. H04-199632 (patent document 1) and No. 2004-320050 (patent document 2) disclose the SOI substrate having such a gettering site. The SOI substrate according to these documents includes the gettering site not in the supporting substrate, but in the insulating layer.
FIG. 4 is a cross-sectional view showing the SOI substrate according to the patent document 1. In the SOI substrate 100, an insulating layer 102, a sink layer 103, another insulating layer 104 and a silicon layer 105 are stacked in this sequence on a supporting substrate 101. Here, the sink layer 103 is constituted as a polycrystalline silicon layer for example, to thereby serve as the gettering site.